Three-dimensional (3D) printing is an additive manufacturing technique enabling creation of an article by forming successive layers of material under computer control to create a 3D structure. The process typically includes selectively heating portions of a layer of powder of the material to melt or sinter the powder to the previously-placed layers to form the article layer by layer. Plastic, ceramic, glass, and metal articles may be formed by 3D printing from powders of plastic, ceramic, glass, and metal, respectively. A 3D printer lays down powder material, and a focused energy source melts or sinters that powder material in certain predetermined locations based on a model from a computer-aided design (CAD) file. Heating methods include direct metal laser melting (DMLM), direct metal laser sintering (DMLS), selective laser melting (SLM), selective laser sintering (SLS), and electron beam melting (EBM). Once one layer is melted or sintered and formed, the 3D printer repeats the process by placing additional layers of material on top of the first layer or where otherwise instructed, one layer at a time, until the entire article is fabricated. 3D printing may be accomplished by powder bed processing or other methods of powder processing.
Metal 3D printing enables manufacturers to create end-use metal articles that often outperform those produced with traditional casting techniques. Once those articles are installed for end-use, they continue to save money because of their light weight, high strength, and precise fit. In conventional article manufacturing, however, achieving high feature fidelity in an article formed by 3D printing may be difficult, if not impossible, without machining the article after formation by printing. For metal articles having features with tolerances in the range of +/−25 μm (+/−1.0 mil), it is not conventionally possible to achieve such high feature fidelity by metal 3D printing alone. The current lower limit is about 76 μm (3.0 mil). In the current conventional metal 3D printers, a single powder hopper and a single powder cut (powder size distribution) is used. A conventional metal powder cut for DMLM has an average particle size of about 30 μm (about 1.2 mil), with the particle size distribution being in the range of about 10 μm to about 45 μm (about 0.4 to about 1.8 mil). Such metal powder cuts are appropriate for build layer thicknesses of about 50 μm (2.0 mil) or greater. In order to achieve tolerances below about 76 μm (3.0 mil) with such build layers, a machining step is required after the metal 3D printing.
Conventional ceramic powder cuts have an average particle size and a particle size distribution similar to conventional metal powder cuts.